The invention relates to gas insulated electrical gear comprising at least one tank filled with a dielectric gas and provided with a rupture disk which ruptures in the event of the dielectric gas in the tank reaching an excessive pressure so as to allow the gas to be exhausted from the tank. The material from which the disk is made can be metal, graphite, or some other material.
Rupture of the disk serving as a pressure discharge device is obtained by making the disk itself fragile, i.e. by making it out of sheeting that is thinner than that of the remainder of the tank.
Such gear is generally situated in an environment that is not protected from bad weather and weather changes, but it can also be installed in a relatively protected environment, e.g. in sheltered premises.
If the rupture disk is not protected from the variations in the temperature of the environment outside the tank, differential expansion takes place between itself and the tank. Such differential expansion can degrade the mechanical performance of the rupture disk in the long run.
In addition, if this disk is not protected from the moisture and/or the pollution of the environment outside the tank, it can be subjected fairly quickly to corrosion phenomena as a result of the moisture or the condensation affecting the outside wall of the tank. Although it is possible to make the rupture disk out of a material that withstands corrosion, such as nickel, that solution remains very expensive. There is another solution which consists in protecting the main disk from external attack by means of a second rupture disk, as described in patent DE 3 743 562. However, that solution is difficult to implement so that rupture takes place correctly, and additional sealing is required to ensure that no external air penetrates into the space between the two rupture disks. Such a configuration is therefore difficult to implement and is expensive.
The object of the invention is to provide a solution that is simple and of relatively low cost for protecting a pressure discharge device against atmospheric attack, the device being a rupture disk installed in gas-insulated electrical gear, for example.
To this end, the invention provides gas insulated outdoor electrical gear comprising at least one tank filled with a dielectric gas and provided with a rupture disk which ruptures in the event of the dielectric gas in the tank reaching an excessive pressure so as to allow the gas to be exhausted from the tank, wherein the rupture disk is protected against attack from the environment outside the tank by being placed inside an enclosed cabinet having an atmosphere in which temperature and humidity are controlled.
This cabinet can advantageously be a low voltage cabinet and/or a cabinet for supporting mechanical controls fitted to said electrical gear. In general, such a low voltage cabinet and/or mechanical control support cabinet is provided to maintain controlled temperature and humidity inside the cabinet. In particular, it is generally fitted with an anti-condensation and/or heating resistance that is controlled as a function of external atmospheric conditions and possibly as a function of the current being carried by the electrical gear on which the cabinet is mounted. Consequently, such a cabinet is well suited to performing the function of protecting a rupture disk against atmospheric attack.
To ensure that the insulating gas of the tank does not pollute the equipment in the cabinet in the event of the disk rupturing, the cabinet can have an opening that is closed by a flap. Thus, gas at excess pressure escapes from the tank because the disk ruptures, and it is guided to the opening of the cabinet by a deflector or an exhaust duct. The opening preferably lies in the top portion of the cabinet so as to reduce the risk of gas being projected towards people close by the cabinet.